Insulating device for a bearing

ABSTRACT

An insulating device for a bearing mountable within a housing, the bearing having an inner ring and an outer ring with an outer circumferential surface and opposing axial ends and a plurality of rolling elements disposed there between. The insulating device comprises: a first annular part, which is adapted to be in contact to the outer circumferential surface of the outer ring, and a second annular part, which is also adapted to be in contact to the outer circumferential surface of the outer ring. The first and second part form the insulation device which is adapted to contact, in an assembled state of the bearing in the housing, both the outer ring and the housing. The first part is thermally conductive and electrically insulating and the second part is electrically insulating and less thermally conductive than the first part or is not thermally conductive.

CROSS REFERENCE OF RELATED APPLICATIONS

This application is based on and claims priority to Italian ApplicationNo. 102019000022320, filed Nov. 28, 2019, under 35 U.S.C. § 119, theentire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates to an insulating device for a bearingmountable within a housing for electrically insulating the bearing fromthe housing.

BACKGROUND

Bearing assemblies are well known and usually comprise an inner ring andan outer ring, wherein a plurality of rolling elements is disposedtherebetween. In case a bearing assembly operates in an electricenvironment, such as an electric motor, damage can occur to the bearingcomponents, when electric current passes through the bearing. To preventsuch a flow of current it is known to provide the bearing rings with aninsulating coating or an insulating encasing.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments in accordance with this disclosure will now be describedwith reference to the appended drawings, which show some non-limitingexamples of embodiment of the disclosure, in which:

FIG. 1 shows an axial cross-sectional view of a bearing arrangementcomprising an insulated bearing which is mounted between a shaft and ahousing in accordance with the present disclosure; and

FIG. 2 shows an enlarged view of the upper portion of the insulatedbearing of FIG. 1.

DETAILED DESCRIPTION

It is known to provide the bearing rings with an insulating coating oran insulating encasing. Disadvantageously, even if the insulatingmaterials used for covering the outer ring of metal bearings are costeffective, they are also thermally insulating which results in anincreased operating temperature of the bearing components and therebyreducing the service life of such a bearing.

Alternatively, it is also known to use so called hybrid bearings,wherein the rolling elements are made from ceramic for providing theelectric insulation and the rings are made from metal for providing aheat transfer. However, hybrid rolling bearings are very costly.

Consequently, embodiments of the disclosure provide a cost-effectiveinsulation device for a bearing, which also allows for a good heattransfer from the bearing to the outside.

In the following, an insulating device for a bearing assembly isdisclosed, wherein the bearing assembly is mountable into a housing. Thebearing assembly usually has an inner ring and an outer ring with anouter circumferential surface and opposing axial ends, and a pluralityof rolling elements are disposed between the inner ring and the outerring. The insulating device further comprises a first annular part whichis adapted to be in contact to the outer circumferential surface of theouter ring, and the second annular part, which is also adapted to be incontact to the outer circumferential surface of the outer ring. Thefirst and the second part form the insulation device and are adapted tocontact, in an assembled state of the bearing in the housing, both theouter ring and the housing.

For electrically insulating the bearing from the housing while notincreasing the operating temperature inside the bearing, the first partis thermally conductive but electrically insulating, wherein the secondpart is electrically insulating, only. A material which is thermallyconductive but electrically insulating is for example ceramic, such asaluminum oxide. An alternative is metal with an insulating coating, e.g.anodized aluminum.

Due to the thermally conductive material of the first part, heat whichaccumulates during operation of the bearing may be transferred from thebearing to the housing. In principle it would be also possible to usethe thermally conductive and electrically insulating material for boththe first and the second part of the insulating device. However, such amaterial is very expensive and difficult to attach to the outer ring.Thus, the second part is made from a less costly but neverthelesselectrically insulating material.

Preferably, the second part is made from a plastic material which isthermally insulating and very cost effective. Plastic material has thefurther advantage that it can be manufactured to different shapes, e. g.by injection molding. Further, it is possible to overmold the ring withthe plastic material. This allows for novel attachment possibilities ofthe insulating device, which will be explained further below.

According to a further exemplary embodiment, the first and second partabut against each other and/or overlap. Thereby, a continuous insulatingdevice may be provided, which covers the complete outer circumferentialsurface of the outer ring. This ensures a continuous electric insulationbetween bearing and housing.

According to the further exemplary embodiment, the first and/or secondpart comprises an axially extending portion having an inner cylindricalsurface, which is adapted to at least partly, contact and/or cover theouter circumferential surface of the outer ring, and a radiallyextending flange portion, which is adapted to at least partly contactand/or cover the axial ends of the outer ring. This design allows theinsulation device to tightly fit onto the outer ring of the bearing, sothat the outer ring is electrically insulated on all sides.Additionally, the radial flange portion may be used for fastening theinsulating device to the outer ring.

It is further advantageous that the axial extending portion of the firstpart has a greater axial length than the axially extending portion ofthe second part. Thereby, an efficient large thermal contact surfacemaybe provided which in turn allows for a sufficient thermalconductivity so that heat does not accumulate in the bearing, but istransferred to the housing.

In a further exemplary embodiment, the first part has a first fasteningstructure and the second part has a second fastening structure, which iscomplementary to the first fastening structure, wherein first and secondfastening structures are designed to fasten the first and second part ina form fit manner. Such a form fit engagement is possible since thematerial of the second part is chosen to be less stiff than the materialof the first part, i.e. the ceramic. Thereby, the first and second partcan be attached to each other in a form fit manner, even if one part ismade from ceramic, which is usually too stiff to be used in a form fitengagement. The complementary fastening structures of the first andsecond part, which provide the form fit, allow for an easy and quickassembling of the insulation device to the bearing assembly. Thereby, itis particularly preferred that the fasting structures of the first andsecond part are formed to have complementary recesses and protrusions,which engage, e.g. snap, into each other.

According to a further exemplary embodiment, the first and/or secondpart further comprises at least one retaining element, which is adaptedto retain the first and/or second part to the outer ring. Besides thefastening of the first and second part to each other it is alsonecessary to provide a member configured to retain the insulating deviceto the bearing itself. Since the outer ring has to be fixed to thehousing in a non-rotatable manner, any intermittently arranged part,such as insulating device, needs also to be fixed to the outer ring andto the housing in a non-rotatable manner, so that no relative motionbetween the insulating device and the outer ring and the housing mayoccur.

For attaching the insulating device to the outer rings, the insulatingdevice preferably further comprises at least one retaining element whichprotrudes radially inwardly and is preferably arranged at the axialextending portion. The protruding element is further adapted to engagewith a recess provided at the outer circumferential surface of the outerring.

As above discussed above, the insulating device is preferably attachedto the outer ring in a simple but secure manner. In the exemplaryembodiment, wherein the second part is made from a slightlyelastic/deformable material, i.e. less stiff material than the ceramicmaterial of the first part, (e.g. plastic), it is preferred to assemblythe outer ring and the insulating device as follows: The first part ofthe insulating device is arranged at the outer ring and then the secondpart is placed at the outer ring and snapped into the fasteningstructure at the first part and, at the same time, snapped into therecess or holding structure at the outer ring Thereby, an insulatedbearing assembly may be provided, which can then be assembled to thehousing/shaft.

A further aspect of the exemplary embodiments relates to an insulatedbearing assembly comprising a bearing, which is mountable within ahousing and has an inner ring and an outer ring, and a plurality ofrolling elements disposed therebetween. Further the outer ring has anouter circumferential surface and opposing axial ends. At the outercircumferential surface of the outer ring an insulating device, asdiscussed above, is arranged and attached. Thereby an insulated bearingassembly maybe provided which allows for an easy attachment of theinsulated device to the bearing and a non-rotatable mounting of thebearing to the housing.

Further exemplary embodiments are defined in the dependent claims aswell as in the description and the figures. Thereby, elements describedor shown in combination with other elements may be present alone or incombination with other elements without departing from the scope ofprotection.

In the following same or similar functioning elements are indicated withthe same reference numerals.

FIG. 1 illustrates a bearing arrangement 100 comprising a bearing 10,which is mounted into a housing 2, and about a shaft 4, for supportingthe shaft 4 rotatably in the housing 2. The housing, 2, the shaft 4, andthe bearing 10 are rotatable about a central axis of rotation AC. Thebearing has an outer ring 12 and an inner ring 14 and a plurality ofrolling elements 16 (balls in the illustrated case) disposed between therings 12 and 14. The outer ring 12 has further an outer circumferentialsurface 18 and opposing axial ends 20, 22 each having radially extendingsurface 24, 26 (see FIG. 2), respectively.

As is further shown in FIG. 1 and in greater detail in FIG. 2, aninsulating device 30 is arranged between the outer ring 12 and thehousing 2. The insulating device 30 prevents an electric current to passfrom the shaft 4, through the bearing 10 to the housing 2. For that, theinsulating device 30 is made from an electrically insulating material.As can be further seen, the insulating device 30 encases the outer ring12 and extends along the outer circumferential surface 18 as well asalong the radial surfaces 24, 26.

The problem with such insulating encasings is that heat, which generatesduring use of the bearing or operation of a machinery which comprisesthe bearing, cannot be transferred from the shaft 4 to the housing 2 andaccumulates in the bearing 10. This in turn decreases the service lifeof the bearing 10, and also of the machinery which comprise the bearing10.

For providing both a secure electrical insulation but also a goodthermal conductivity, an insulating device 30 is provided which has twoparts 32 and 34. The first part 32 extends along the outercircumferential surface 18 of the outer ring and is made from athermally conductive and electrically insulating material, e.g.,ceramic. The second part 34 also extends along the outer circumferentialsurface 18, and is made from an electrically insulating material, e.g.,plastic, only that is not considered thermally conductive. In variousembodiments in accordance with disclosure, the second part 34 is lessthermally conductive than the first part 32. Alternatively, in someembodiments the second part 34 is made of an electrically insulating andthermally conductive material, e.g., ceramic, while the first part 32 ismade of an electrically insulating material that is less thermallyconductive than the second part 34.

In principal it could be also possible to make the complete insulatingdevice 30 from the thermally conductive and electrically insulatingmaterial. However, this is very costly, and, in case ceramic is used,requires a sophisticated manufacturing process. Since ceramic is verystiff, an insulating device only made from ceramic needs to be preciselysized to the dimensions of the outer ring. Additionally, it is necessaryto attach the insulating device securely to the outer ring, so that anon-rotatable attachment of the outer ring to the housing can beprovided. This in turn requires that the insulating device is alsonon-rotatably attached to the outer ring and/or to the housing. In casethe insulating device is made from ceramic such an attachment cannot beguaranteed.

Consequently, the second part 34 is made from a second material, whichis electrically insulating but may be less stiff than ceramic, e.g. aplastic material, which in turn allows for both an easy manufacture anda secure and non-rotatable attachment of the insulating device to theouter ring. The second material or the plastic, respectively, may be aresilient material, or at least a slightly deformable material, so thatthe second part 34 may be attached to the first part 32 and/or to theouter ring 12, without breaking.

For fixing the first and second parts 32, 34, the first and second partcomprises fastening structures 36, 38. In the illustrated non-limitingembodiment, the fastening structure 36 of the first part 32, is designedas groove 40 and a nose 42. The groove 40 extends radially outwardlyfrom an inner circumferential surface 44 of the first part 32, whichcontacts the outer circumferential surface 18 of the outer ring 12, andis axially limited by the nose 42. The groove 40 and the nose 42 aredesigned such that the fastening structure 38 of the second part 34 maybe snapped into. For that, the fastening structure of the second part 34comprises a correspondingly and complimentarily designed groove 46 andnose 48, wherein the nose 48 of the second part 34 may be snapped intothe groove 40 of the first part 32, and the nose 42 of the first part 32may be snapped into the groove 46 of the second part 34. This ensures anaxial and radial attachment of the first and second part 32, 34 forforming the insulating device 30. In order to fasten the first andsecond part 32, 34 also in circumferential direction, the groove 40and/or the groove 46 of the second part are not designed as continuouslyannular grooves, but are provided as discrete recesses, whichaccommodate discrete protruding nose elements.

Besides fastening the first and second part 32, 34 to each other, it isalso necessary to attach the insulating device 30 as such to the outerring 12, preferably in a non-rotatable manner.

For that, both the first and the second part 32, 34 each have a radiallyextending flange portion 50, 52, which extends along the axial ends 20,22 of the outer ring 12, respectively. In an assembled state—namely withthe complementary fastening structures 36, 38 being engaged, the radialflange portions 50, 52 contact and abut against the radially extendingsurfaces 24 and 25 of the outer ring 12, and thereby prevent any axialmovement of the insulating device 30.

Additionally, the insulating device 30 may have retaining means forretaining the insulating device to the outer ring 12. In the illustratedembodiment of FIGS. 1 and 2, the outer ring 12 is equipped with a recess54, and the second part 34 comprises a further nose 56, wherein the nose56 and the recess 54 are engaged. This allows for a strong couplingbetween insulating device 30 and outer ring 12 and ensures a secureattachment of the insulating device 30 to the outer ring 12. Foravoiding any circumferential movement of the insulating device inrelation to the outer ring 12, nose 56 and recess 54 may be designed asdiscrete elements.

The radial movement is also prevented since the insulating device 30 isarranged between and contact both the housing 2 and the outer ring 12.

As can be further seen from the illustrated embodiments, the first part32 has an outer circumferential surface 60 which is in contact with aninner circumferential surface 6 of the housing 2. This contact allowsfor a heat transfer between the bearing 10 and the housing 2. Forproviding a very good heat transfer, a length L of the first part 32 andparticularly of the outer circumferential surface 60 of the first part32 is maximized. As illustrated, the outer circumferential surface 60extends over almost the complete length LB of the bearing 10, whichprovides sufficient thermal contact for providing an optimized heattransfer from the bearing 10 to the housing 2. In some embodiments thelength L is greater than 50% of the length of LB. In some embodiments,length L is between 50-99% of the length of LB. In some embodiment,length L is between 51-99% of the length of LB. In some embodiment,length L is between 60-90% of the length of LB. In some embodiments,length L is between 70-90% of the length of LB. In some embodiments,length L is between 75%-95% of the length of LB. In some embodiments,length L is between 80%-95% of the length of LB. In some embodiments,length L is between 80%-90% of the length of LB. In some embodiments,length L is about 60% of the length of LB. In some embodiments, length Lis about 75% of the length of LB. In some embodiments, length L is about80% of the length of LB. In some embodiments, length L is about 85% ofthe length of LB. In some embodiments, length L is about 88% of thelength of LB. In some embodiments, length L is about 91% of the lengthof LB. In some embodiments, length L is about 95% of the length of LB.In some embodiments, length L is about 98% of the length of LB.

In summary by providing an insulating device which has two parts madefrom different materials, wherein only one material is thermallyconductive, an insulated bearing assembly can be provided which allowsfor a good thermal management, good electric insulation and is costeffective and easy to manufacture.

There are numerous other variants in addition to the embodimentsdescribed above. Furthermore, said embodiments are merely examples thatlimit neither the scope nor the application nor the possiblearrangements of the invention. Indeed, although the above descriptionenables the person skilled in the art to carry out the present inventionaccording to at least one example embodiment thereof, many variants ofthe described components can also be used without thereby moving outsidethe scope of the invention as defined in the attached claims, whichshould be understood literally and/or according to the legal equivalentsthereof.

REFERENCE NUMERALS

-   100 bearing assembly-   2 housing-   4 shaft-   6 inner circumferential surface of the housing-   10 bearing-   12 outer ring-   14 inner ring-   16 rolling elements-   18 outer circumferential surface-   20, 22 axial ends-   24, 26 radially extending surfaces-   30 insulating device-   32 first part-   34 second part-   36, 38 fastening structures-   40 groove-   42 nose-   44 inner circumferential surface-   46 groove-   48 nose-   50, 52 flange portions-   54 recess-   56 nose-   60 outer circumferential surface-   L length of first part-   LB length of bearing

What is claimed is:
 1. An insulating device for a bearing mountablewithin a housing, the bearing having an inner ring and an outer ringwith an outer circumferential surface and opposing axial ends and aplurality of rolling elements disposed therebetween, wherein theinsulating device comprises: a first annular part, which is configuredto be in contact with the outer circumferential surface of the outerring; and a second annular part, which is configured to be in contactwith the outer circumferential surface of the outer ring, wherein thefirst annular part and second annular part form the insulation devicewhich is configured to contact, when in an assembled state, both theouter ring and the housing; wherein the first annular part is thermallyconductive and electrically insulating, and the second annular part iselectrically insulating; wherein the material of the second annular partis thermally insulating.
 2. The insulating device according to claim 1,wherein a material of the first annular part is a ceramic material. 3.The insulating device according to claim 2, wherein the ceramic materialis aluminum oxide.
 4. The insulating device according to claim 1,wherein the first annular part is made from a metal with an insulatingcoating.
 5. The insulating device according to claim 4, wherein theinsulating coating is anodized aluminum.
 6. The insulating deviceaccording to claim 1, wherein the material of the second annular part isa plastic material.
 7. The insulating device of claim 6, wherein theplastic material is injection molded or over-molded.
 8. The insulatingdevice according to claim 1, wherein the first and/or second annularparts comprise an axially extending portion having an inner cylindricalsurface which is configured to at least partly contact and/or cover theouter circumferential surface of the outer ring, and a radiallyextending flange portion which is configured to at least partly contactand/or cover the axial ends of the outer ring.
 9. The insulating deviceaccording to claim 1, wherein at least one of the first annular part andthe second annular part further comprises at least one insulating deviceretainer.
 10. The insulating device according to claim 9, wherein the atleast one insulating device retainer is a protruding element which isarranged on the axially extending portion and protrudes radiallyinwardly, and is configured to be received in a recess provided at theouter circumferential surface of the outer ring.
 11. An insulatingdevice for a bearing mountable within a housing, the bearing having aninner ring and an outer ring with an outer circumferential surface andopposing axial ends and a plurality of rolling elements disposedtherebetween, wherein the insulating device comprises: a first annularpart, which is configured to be in contact with the outercircumferential surface of the outer ring; and a second annular part,which is configured to be in contact with the outer circumferentialsurface of the outer ring, wherein the first annular part and secondannular part form the insulation device which is configured to contact,when in an assembled state, both the outer ring and the housing; whereinthe first annular part is thermally conductive and electricallyinsulating, and the second annular part is electrically insulating;wherein the first annular part has a first form fit fastener and thesecond annular part has a second form fit fastener, which iscomplementary to the first form fit fastener.
 12. The insulating deviceaccording to claim 11, wherein the first and second form fit fastenerscomprise corresponding and complimentary protruding elements andrecesses.
 13. An insulated bearing assembly comprising: a bearingmountable within a housing; wherein the bearing has an inner ring and anouter ring and a plurality of rolling elements disposed therebetween;wherein the outer ring has an outer circumferential surface and opposingaxial ends; and an insulation device on the outer circumferentialsurface of the outer ring; wherein the insulating device comprises: afirst annular part, which is configured to be in contact to the outercircumferential surface of the outer ring, and a second annular part,which is also configured to be in contact to the outer circumferentialsurface of the outer ring, wherein the first annular part and secondannular part form the insulation device which is configured to contact,in an assembled state of the bearing in the housing both the outer ringand the housing; wherein the first annular part is thermally conductiveand electrically insulating, and the second annular part is electricallyinsulating and less thermally conductive than the first annular part.14. The insulated bearing assembly according to claim 13, wherein thefirst and/or second annular parts comprises an axially extending portionhaving an inner cylindrical surface which is configured to at leastpartly contact and/or cover the outer circumferential surface of theouter ring, and a radially extending flange portion which is configuredto at least partly contact and/or cover the axial ends of the outerring.
 15. The insulated bearing assembly insulated bearing assemblyaccording to claim 14, wherein the axially extending portion of thefirst annular part has a greater axial length (L) than the axiallyextending portion of the second annular part.
 16. The insulated bearingassembly according to claim 13, wherein the first annular part has afirst form fit fastener and the second annular part has a second formfit fastener, which is complementary to the first form fit fastener. 17.An insulating device for a bearing mountable within a housing, thebearing having an inner ring and an outer ring with an outercircumferential surface and opposing axial ends and a plurality ofrolling elements disposed therebetween, wherein the insulating devicecomprises: a first annular part, which is configured to be in contactwith the outer circumferential surface of the outer ring; and a secondannular part, which is configured to be in contact with the outercircumferential surface of the outer ring, wherein the first annularpart and second annular part form the insulation device which isconfigured to contact, when in an assembled state, both the outer ringand the housing; wherein the first annular part is thermally conductiveand electrically insulating, and the second annular part is electricallyinsulating; wherein the first and second annular parts are configured toat least abut against each other.
 18. An insulating device for a bearingmountable within a housing, the bearing having an inner ring and anouter ring with an outer circumferential surface and opposing axial endsand a plurality of rolling elements disposed therebetween, wherein theinsulating device comprises: a first annular part, which is configuredto be in contact with the outer circumferential surface of the outerring; and a second annular part, which is configured to be in contactwith the outer circumferential surface of the outer ring, wherein thefirst annular part and second annular part form the insulation devicewhich is configured to contact, when in an assembled state, both theouter ring and the housing; wherein the first annular part is thermallyconductive and electrically insulating, and the second annular part iselectrically insulating; wherein the first and second annular parts areconfigured to overlap.
 19. An insulating device for a bearing mountablewithin a housing, the bearing having an inner ring and an outer ringwith an outer circumferential surface and opposing axial ends and aplurality of rolling elements disposed therebetween, wherein theinsulating device comprises: a first annular part, which is configuredto be in contact with the outer circumferential surface of the outerring; and a second annular part, which is configured to be in contactwith the outer circumferential surface of the outer ring, wherein thefirst annular part and second annular part form the insulation devicewhich is configured to contact, when in an assembled state, both theouter ring and the housing; wherein the first annular part is thermallyconductive and electrically insulating, and the second annular part iselectrically insulating; wherein the first and/or second annular partscomprise an axially extending portion having an inner cylindricalsurface which is configured to at least partly contact and/or cover theouter circumferential surface of the outer ring, and a radiallyextending flange portion which is configured to at least partly contactand/or cover the axial ends of the outer ring; wherein the axiallyextending portion of the first annular part has a greater axial length(L) than the axially extending portion of the second annular part.